Digital subscriber line (xDSL) communication can provide a high bandwidth data path supported by the twisted pair wiring infrastructure of the public switch telephone network (PSTN). xDSL technology supports data service simultaneously with traditional telephone service using a separation technique. Suitable xDSL technologies include asymmetric digital subscriber line (ADSL), rate adaptable digital subscriber line (RADSL), symmetric digital subscriber line (SDSL), high speed digital subscriber line (HDSL), very high speed digital subscriber line (VDSL) and other such digital subscriber line technologies.
In general, an xDSL communication link can be established across the local loop between customer premises equipment (CPE) and a local loop termination point (e.g., central office or remote terminal). The local loop termination point typically includes an xDSL access multiplexer (DSLAM) which handles the xDSL link on the network side. The customer premises equipment typically includes one or more xDSL termination units (XTUs) which handle the xDSL link on the customer premises side. One architecture for xDSL communication is disclosed in U.S. Pat. No. 5,668,857, entitled “Communication Server Apparatus and Method.”
In the system disclosed in U.S. Pat. No. 5,668,857, for example, it can be important for the customer premises equipment to signal the DSLAM when the customer premises equipment desires a connection to a termination unit (e.g., modem) within the available pool of units. In response, the DSLAM needs to have a means for providing a special signal back to the customer premises equipment which does not interfere with ongoing voice traffic.